The Top 100 Most Cited Journal Articles on Hydrocephalus

Hydrocephalus represents a significant burden of disease, with more than 383,000 new cases annually worldwide. When the magnitude of this condition is considered, a centralized archive of pertinent literature is of great clinical value. From a neurosurgical standpoint, hydrocephalus is one of the most frequently treated conditions in the field. The focus of this study was to identify the top 100 journal articles specific to hydrocephalus using bibliometric analysis. Using the Journal of Citation Report database, 10 journals were identified. The Web of Science Core Collection was then searched using each journal name and the search term “hydrocephalus.” The results were ordered by “Times Cited” and searched by the number of citations. The database contained journal articles from 1976 to 2021, and the following variables were collected for analysis: journal, article type, year of publication, and the number of citations. Journal articles were excluded if they had no relation to hydrocephalus, mostly involved basic science research, or included animal studies. Ten journals were identified using the above criteria, and a catalog of the 100 most cited publications in the hydrocephalus literature was created. Articles were arranged from highest to lowest citation number, with further classification by journal, article type, and publication year. Of the 100 articles referenced, 38 were review articles, 24 were original articles, 15 were comparative studies, 11 were clinical trials, six were multi-center studies, three were cross-sectional, and three were case reports with reviews. Articles were also sorted by study type and further stratified by etiology. If the etiology was not specified, studies were instead subcategorized by treatment type. Etiologies such as aqueductal stenosis, tumors, and other obstructive causes of hydrocephalus were classified as obstructive (n=6). Communicating (n=15) included idiopathic, normal pressure hydrocephalus, and other non-obstructive etiologies. The category “other” (n=3) was assigned to studies that included etiologies, populations, and/or treatments that did not fit into the classifications previously outlined. Through our analysis of highly cited journal articles focusing on different etiologies and the surgical or medical management of hydrocephalus, we hope to elucidate important trends. By establishing the 100 most cited hydrocephalus articles, we contribute one source, stratified for efficient referencing, to facilitate clinical care and future research on hydrocephalus.


Introduction And Background
Hydrocephalus is the pathologic accumulation of excess cerebrospinal fluid (CSF) within the calvaria, brain parenchyma, or intraventricularly [1].The divergence in anatomical designation among existing literature can be further elucidated with the following definition: "Hydrocephalus is an active distension of the ventricular system of the brain resulting from inadequate passage of CSF from its point of production within the cerebral ventricles to its point of absorption into the systemic circulation" [2].This broader classification mirrors the variation in the clinical picture of hydrocephalus.On presentation, patients can assume an array of symptoms, with underlying etiologies including increased CSF production, decreased CSF absorption, or obstructed flow from the ventricles to the subarachnoid space [1][2][3].This great variability can elicit further complexity for clinicians and researchers managing and studying this condition.
Many journal articles have been published about hydrocephalus.One way to analyze the impact of these publications is to use citation analysis.Bibliometric analyses using online databases such as the Web of Science Core Collection have systematized the influx of medical and biological publications during this information era [4,5].The earliest database to track citations was developed in 1962 by the Institute for Science Information, which was later combined with the Social Sciences Index in 1973 and the Arts and Humanities Citation Index in 1978 to create a comprehensive database.This merged database was presented online in 1997 under the name Web of Science, which would later become the Web of Science Core Collection [6].Recent publications have evaluated relevant work in different fields through citation analysis.For example, articles summarizing the most cited research in pediatric neurosurgery, orthopedic surgery, urethral reconstruction, epilepsy, and status epilepticus have contributed to the literature [6][7][8][9][10].In this review, we present the 100 most highly cited journal articles about hydrocephalus published in ten journals,

Sources and Citations
Ten journals were identified (Table 1) using the selection criteria outlined above, and articles were sorted from highest to lowest in citation number, with the search returning 1,554 results.The impact factor of the journals identified in the Journal of Citation Reports ranged from 0.985 to 7.124.Thirty-six percent of articles were published in journals with an impact factor greater than 5, while 52% were found in journals with an impact factor of 1-5, and 12% were found in journals with an impact factor under 1.Among the 100 journal articles selected, 33

Type and Field of Study
Articles were also distinguished by study type, as indicated by PubMed or evidenced in the article, and further stratified by etiology.If the etiology was not specified, studies were instead subcategorized by treatment type (Table 3).Pediatric studies (n=14) included those specific to the pediatric population and were separated from articles concerning infants (n=9) and pediatric studies not further classified by etiology.Etiologies such as aqueductal stenosis, tumors, and other obstructive causes of hydrocephalus were classed as obstructive (n=6).Communicating (n=15) included idiopathic, normal pressure hydrocephalus, and other non-obstructive etiologies.The category "other" (n=3) was assigned to studies that included etiologies, populations, and/or treatments that did not fit into the classifications previously outlined.Of the 100 articles referenced, 38 were review articles, 24 were original articles, 15 were comparative studies, 11 were clinical trials, six were multi-center studies, three were cross-sectional, and three were case reports with reviews.Original prospective non-review articles and retrospective reviews accounted for more than half of the selected articles.Posthemorrhagic and communicating hydrocephalus were the most commonly cited by etiology (n=15).Concerning treatment, the most frequently cited subcategory was shunt-related articles (n=19).Comparative studies and clinical trials were most frequent in articles relating to shunts (n=4 and n=5, respectively).Cross-sectional studies were most common in articles specific to pediatrics (n=2) and multicenter studies (n=4).Case reports appeared most often in relation to posthemorrhagic studies (n=2).

Discussion
Hydrocephalus represents a significant burden of disease, as substantiated by the estimated regional incidence in 2018 of 68 per 100,000 births in the US/Canada and the more than 383,000 new cases annually worldwide [111].Its epidemiological impact translates to the clinical realm, heightening the urgency for understanding and managing hydrocephalus.From a neurosurgical standpoint, hydrocephalus is one of the most frequently treated conditions in the field, and its impact is great [30].Given this, a centralized archive of pertinent literature is of great clinical value.Consistent with several new publications focusing on highlycited literature within neurosurgery, we aimed to generate a list of the most relevant works on hydrocephalus published during the last four and a half decades [6,7].Using bibliometric analysis, we created a catalog of the 100 most cited publications specific to hydrocephalus literature.We then further subcategorized our results by journal, article type, publication year, and number of citations.By analyzing highly cited journal articles, we have outlined critical reference sources and highlighted important trends throughout the literature.The exclusion of articles unrelated to hydrocephalus, those based on basic science research, and those including animal studies maintained our intention to consider the scope of hydrocephalus in the context of clinical neurosurgery.With this aim, we focused on different etiologies of this pathology alongside the surgical or medical management of hydrocephalus.
Ponce and Lozano demonstrated the importance of recognizing highly-cited literature in neurosurgery overall [6].Wilcox et al. and, more recently, Grayson et al. extended their work and continued to focus on broader areas of study such as neurosurgery and, alternatively, pediatric neurosurgery [7,112,113].The feasibility of this form of analysis can also be demonstrated with a more targeted focus on conditions and treatments frequently encountered in neurosurgery and neurosurgical research.The field of citation analysis has grown over the past decade since Ponce and Lozano originally published their article and has grown to include many topics within the field of neurosurgery, such as trigeminal neuralgia, stereotactic radiosurgery for meningioma, and spinal deformity [114][115][116].There are multiple ways of interpreting the data, including by country, institution, and authorship.The impact factor of selected journals and the number of highly cited works in each journal were also analyzed, with 88% of highly cited papers being found in journals with an impact factor greater than 1.Multiple authors in the literature have debated the importance of impact factors, with journals assigned higher impact factors believed to attract papers of higher quality.This may not reflect the quality of the peer review process or the content of the journal [117,118].It has also been proposed that journals publishing more review articles achieve higher impact factors due to the nature of review papers being cited more frequently than other types of research articles [119].This was also seen in our literature review, with 33% of highly cited papers being reviews compared to 24% of original articles and 15% of comparative studies being the other highly cited journal article categories.
The list of most cited works in descending order of citation number is led by a randomized trial published in 1998 with 469 citations to assess the design of CSF shunt valves in pediatric hydrocephalus.Published in Neurosurgery, this article holds relevance for neurosurgeons, neurosurgical trainees, neuroradiologists, pediatricians, and any student of the neuroanatomical relationship that gives rise to the pathophysiology of hydrocephalus.When viewing the works listed in this manner, it may be beneficial to future surveyors of neurosurgical publications to analyze trends between top-cited lists.Such reviews may compare top-cited works on hydrocephalus, pediatric neurosurgery, and/or other pertinent pediatric neurosurgical pathology to understand how the most relevant works have molded current practices and guided the knowledgebase of today's neurosurgical trainees.With our top 10 most cited papers being published between 1985 and 2005, nearly two decades ago, this type of comparative review of relevant works over time would provide an interesting and informative direction for future similar pieces in the field.As the complexity of this pathology often requires a multidisciplinary care approach to provide the best long-term outcomes for these patients, this method of analysis will better serve the neurosurgical teams and other clinical subspecialties in the care of these patients.By establishing the 100 most cited hydrocephalus articles, we contribute one source, stratified for efficient referencing, to facilitate the exchange of knowledge, clinical care, and future research on hydrocephalus.

Limitations
Citation analysis is not without limitations; the correlation between the number of citations and the impact of a journal article has been debated [5].The journals selected for analysis do not cover all journals in which highly cited articles can be published, and high-impact articles could have been missed.Owing to the time bias of citations, more recent papers have had less time to accumulate citations than older articles [120].This sum of works is thus not a true rank list but rather a collection of the greatest hits.There are also limitations within the database used to research citations; the Web of Science Core Collection only includes articles from 1976 to 2021, so earlier influential journal articles are unlikely to be well represented within the search.Other databases, such as Microsoft Academic and Google Scholar, contain more citations than the Web of Science Core collection, so they could be alternative sources for citation data [4].

Conclusions
This study identified the 100 most cited journal articles on hydrocephalus from journals selected using the Journal Citation Reports database.Bibliometric analysis using the Web of Science Core Collection was used to identify the highest-impact articles based on the number of reported citations.While this analysis does not guarantee flawless determination of the impact and quality of publications, it allows published data to be easily referenced so that clinicians and researchers can identify meaningful research and cases in the study and treatment of hydrocephalus.

FIGURE 1 :
FIGURE 1: Chart depicting journal selection and search criteria were published in the Journal of Neurosurgery, 31 in Neurosurgery, 12 in Pediatric Neurosurgery, nine each in the Journal of Neurosurgery Pediatrics and Child's Nervous System, three in Pediatrics, two in the Journal of Pediatrics, one in World Neurosurgery, and none in either Neuropediatrics or Child's Brain.The 100 most cited papers on hydrocephalus were then listed (Table 2), ranked from highest to lowest number of citations.The article name, associated journal, and year of publication were listed as well.doi:10.3171/jns.1988.69.6.0883[110] Journal of Neurosurgery 1988